Shell molding apparatus



April 10, 1956 R. HURST SHELL MOLDING APPARATUS Filed July 28, 1952 0 4 T 1 /4 w H u m E n M H h u PM w t. X/ 'l m ROSCH/LD HURST INVENTOR. 56. 2'77 BY ATTORNEYS United States Patent 2,741,005 SHELL MOLDING APPARATUS Roschild Hurst, Detroit, Micln, assignor to Ford Motor This application deals with the metal founding art and more specifically with an apparatus for the machine production of shell molds.

Commercially it has been found necessary to make the production of shell molds completely automatic. in order to reduce costs to an acceptable level. This automation has been accomplished and involves a machine in which a metal pattern and a metal sand container co-operate in a definite manner. p r l At the beginning of'the operation the metal box in which the sand is held is positioned with its top open. The heated metal pattern is then inverted and positioned so that the pattern plate closes the open top of the box and the patterns proper are within the box. The entire assemblage is then rotated through 180 degrees to shower the heated pattern with the falling, sand. After a few seconds the box assembly is again rotated through 180 degrees and the heated metal pattern with'the adhering raw shell mold is removed.

When machines of this type were first constructed, difliculty was encountered due to the tendency of underheated portions of the sand to clump together. Whenever one of these clumps began imbedding in the shell mold near the surface of the mold attacked by the metal, a defective casting inevitably resulted.

The instant invention has been developed to avoid this difiiculty and is best understood by a study of the drawing, in which:

Figure 1 is a sectional view of the sand box.

Figure 2 is a plan view of this box and Figure 3 is a horizontal section of the sand box taken on the line 3-3 in Figure 1.

In Figure 1 the sand box is indicated generally at 10. This sand box comprises heavy mild steel sides 11 and bottom 12. Sides 11 are tapered at the upper end to accommodate the pattern plate. In sloping'edge 13 there is inserted an elastomer strip 14 to permit mechanical mismating of the box and pattern plate without damage to the handling mechanism. Box is supported yieldingly by members 15 which form no part of the instant invention and will not be described here in detail.

Intermediate the top and bottom of box 10, screen 16 is secured by bolts 17. Weight 18 is secured to the center of bottom 12 by chain 19 and bolt 20. The particular method with which this screen is fastened is seen to better advantage in Figure 3 which as stated above, is a horizontal section taken along the line 3-3 of Figure 1. Member 21 shown in Figures 2 and 3 forms a part of the inverting mechanism and need not be further described here. In Figure 2 the elastomer strip 14 is shown on all. four sides 11 of sand box 10.

The presence of the screen 16 prevents lumps which form in the sand from passing through onto the pattern when sand box 10 is inverted. The weight 18 suspended on chain 19 serves a dual function. It prevents the adhesion of the fine sand to the walls and bottom of sand box 10 when'it is inverted and hence quickly showers the pattern with sand. It also serves the purposeof mechanically breaking up any lumps of sand which may form.

While a radical improvement may be obtained by any reasonable weight and chain arrangement, it has been found that a 2 /4 inch square steel cube suspended from a chain of three links secured directly in the center of bottom 12 of the rectangular core box Works best in practice. The outside dimension of this core box is slightly over nine inches. These specific dimensions are given only as exemplary of successful practice and are notto be construed 'as limiting upon the scope of the invention. Screen 16 has been found to be more satisfactorily formed of ordinary V; inch galvanized wire clo'thor rat mesh. 1

I claim as my invention: V

1. In a shell molding machine an invertible sand box closed on all but one side, a weight secured to the side of. the box opposite the open side by a flexible tension member, a screen parallel to the open side of the box and intermediate the weight and box opening and a pattern plate releasably closing the open side of the box.

2. In a shell molding machine an invertible sand box closed onvall but one side, a screen within the box parallel to the open side of the box and removed from such open side, a weight tethered within the space enclosed by the box and screen so that contact between the screen and weight is not possible, and a pattern plate releasably closing the open side of the box.

3. In a shell molding machine, an invertible sand box closed on all but one side, a screen within the sand box dividing the sand box into a section adjacent the open side and a sectionremote from the open side, a weight tethered within the section of the sand box remote from the open end so that contact between the screen and weight is not possible, and a pattern plate closing the open side of the box.

References Cited in the file of this patent UNITED STATES PATENTS Knies Nov. 5, 1935 Barr Dec. 6, 1949 OTHER REFERENCES 

